1. Technical Field
The invention relates to an optical signal transmitting apparatus, an optical signal transmitting device, and an optical signal receiving device.
2. Related Art
In recent years, with rapid development of a digital information processing technique, a demand for high speed, large capacity, and high reliability of a digital communication technique have been increased. Electric signal transmission using a printed-wiring board or a metal electric wire has its limits in data transmission speed and transmission distance because of degradation of a signal quality or an influence of electromagnetic noise. In order to solve these limits, an optical communication technique has been developed and has been put into practical use in various fields.
For example, in the case where signals are transmitted at high speed in the printed-wiring board, impedance mismatch may occur between an element such as an electronic component and a wiring. If such impedance mismatch occurs, signals may be reflected in a terminal of the wiring, thereby degrading signal waveforms. Accordingly, it cannot be expected to perform high-reliable signal transmission.
Generally, the characteristic impedance of the printed-wiring board depends on the width of a transmission line, an interlayer distance, and electric permittivity of a board material. However, in recent years, it is apt to be difficult to achieve the characteristic impedance matching because of multilayered board, high density, and non-uniformity of the terminal of an element.